Passengers on the Victoria line can expect disruptions over the next three years.
Transport for London (TfL) has announced it will upgrade stations, tracks, trains and signalling across the line, including Victoria and Pimlico stations.
TfL says the work, which will be completed by 2012, will increase the number of trains per hour and help reduce journey times.
A spokeswoman for TfL said: "Demand shows no signs of slowing down so work is urgently required to upgrade the Underground's infrastructure, in order to meet current and future transport needs.
"It's important that the upgrade programme is done, however we understand this can cause disruption and therefore frustration to passengers and residents in the borough."